Electric telephone



(No Model.) W. L. RICHARDS. ELECTRIC TELEPHONE.

No. 521,220. Patented June 12, 1894.

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NITED STATES PATENT OFFICEG WILTON L. RICHARDS, OF MALDEN, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

ELECTRIC SPECIFICATION forming part of Letters Patent No. 521,220, dated June 12, 1894. Application filed December 14,1893. Serial No.4:93,660. (No model.)

. transmitters in which the variable resistance medium is a mass of finely divided carbon or other conducting material held between two electrodes; and more particularly to that class of instrument in which the said medium is contained in a chambered block, technically known as a button.

.For the transmission of music as from an orchestra, or from a chorus upon a theater stage, it has been found necessary to employ a transmitter so designed that, while extremely sensitive to sounds originating at some, distance from the instrument, it shall at the same time remain uninjured by powerful tones originating in its immediate vicinity. Transmitters for this class of work must moreover be so constructed that while competent to respond perfectly and faithfullyto the relatively feeble tones of such instruments as the violin, they will not be adversely or abnormally affected by the soundsv produced by more powerful instruments such as drums, or the heavy wind instruments of a brass band. In addition to these requirements it is also desirable that in the operation of such a transmitter all tones of its own shall be suppressed, so that there shall be no resonance or sympathetic vibration of the transmitter as a whole, or of any of its parts.

Theobject of this invention is to provide a transmitter in which the above requirements are met. To this end, I employ slate as the material for the casing and side wall of the variable resistance button, and thereby am enabled to form a button which remains efficient through a wide range of tempera erably of wood, which is stiffened and enabled to preserve its shape by a ring of brass or other metal secured thereto. Thesaid wooden diaphragm-is preferably encircled by a rubber band, and is retained in place by spring pressure, much in the same way as is the diaphragm of the Blake transmitter.

In the drawings which accompanyand illustrate this specification, Figure 1 is a perspective view of an instrument embodying these features, and meeting the above stated requirements; and the transmitter is shown source of current and areceiving telephone. Fig. 2is a central cross section of such a transmitter; and Fig. 3 is a detail showing the outer side of the front or vibratory elec-- trode, secured to the flexible gauze disk, and provided at its center with a bolt whereby it is adapted to be attached to the diaphragm center.

Referring to the drawings a frame R of wood is stifiened and maintained in shape by a metal ring R screwed or otherwise fastened to its back surface; and may be flared as shown on one side, and shouldered on the other toform a ring seat for the diaphragm.

D is a comparatively large diaphragm of Wood encircled by the rubber band '1' in a manner well understood, and retained in said ring seat by the dampening springs d, in much the same way that is employed in holding the diaphragm of the well known Blake transmitter. I have found a diaphragm having a width of' three and one half inches to operate satisfactorily.

The remaining operative portions of the transmitter are combined in a button of the same general type as that which is described and claimed in Letters Patent granted to AnthonyO. White, November 1, 1892, No. 485,311, but differing in some degree structas being in an electric circuit including a urally, and being mounted in an essentially and radically different manner.

The external appearance of the button Bis indicated by Fig. 1, and its internal parts appear in section in Fig. 2. As the transmitter is, in the use for which it is primarily designed, subjected to great variations in temperature,'due both to the current employed in its operation and to the heat from the lights which illuminate the stage it has been found useful to employ slate as the material for the button casing, and for the side wall of the containing chamber formed in the interior of said button. Accordingly, I employ a casing of that material and form in one side thereof the cavity 0 to serve as a containing chamber for the finely divided conducting material which serves as a current changer or variable resistance. Secured to the rear surface of the chamber 0 is the fixed orback electrode e, which is conductively united to a metal nipple y extended through the back of the slate casing and terminating in a socket pin y The front or vibratory electrodef is secured to the center of the inner surface of a flexible or resilient disk g, which in turn is clamped by a metal ring and suitable screws to the front edge of the slate casing. Both electrodes are disks of carbon, but other material such as metal may, if desired, be employed. Electrodes of brass may for example be used, and should preferably be plated with gold. The containing chamber C is thus provided with a circumferential side wall of slate, with a rigid and conducting rear wall formed by the fixed electrode and with an elastic and conductive front wall formed by the vibratory electrode.

The current changing material M is placed within the chamber 0, and is afiuely divided or granulated conducting substance; carbonized anthracite being preferably employed.

In order that the pressure of the air may be equal on both sides of the front electrode, I form the flexible disk g of extremely fine wire gauze, and between the under surface thereof, and the surface of the slate casing to which it is secured, a very thin washer of porous paper is preferably interposed which serves as a cushion without materially hindering the sufficient passage of air. The said gauze disk g supports the front electrode, and completely closes the front of the chamber, retaining the granular conducting material in the said chamber between the electrodes. The said disk 9 is secured to the front electrode by means of a clamping plate 1) on its reverse side which is screwed to a stud g attached to the back of said electrode and projecting through the center of the disk. The stud g by means of a small bolt 19 forming a continuation thereof passing through the center of the diaphragm and secured on the outer side thereof by nuts n in a manner well understood, serves also to attach the front electrode, and thereby the button B as a whole to the said diaphragm so as to participate in its vibrations. A light metal bridge Z) mounted by its feet 11 on the diaphragm spans the back of the button B and a screw socket 0 adjustable by a jam nut O is carried at its center, and delicately supports the socket pin 'y of the button as shown. It will be evident.

therefore that the compound button B instead of being immovably secured by the attachment of its casing to rigid frame portions of the instrumentas is the case in the principal example of the White patent before mcntioned, is mounted wholly but loosely upon the diaphragm itself; and that the light bridge 12 and its socket connection 0 serve merely to support it in place, and to aid in preserving perfect parallelism of the electrodes.

The instrument when in use may, as shown, be suspended by a light stirrup s from cords or chains, or wires S, the said stirrup engaging with hooks, pins, or screws s fixed on the frame ring R. One of the circuit wires to is to be connected with the front, and the other ta with the back electrode. Any metal strip or ribbon m extending from the metal clam ping plate 19 to the frame may be used to establish the front electrode connection, While the wire to may be attached atac to the bridge foot I) as shown, or, if preferred, the said wire may be attached, (say by soldering) directly to the nipple y which projects through the back of the button casing. The said wires w and'zr are'shown as forming the circuit of a source of current E such as a voltaic battery, which circuit includes the transmitter button 13 and a telephone receiver t. Considering now the compound button B with reference to its mounting, it is evident that the front electrode is rigidly attached by means of nuts to the wooden diaphragm, while the back electrode rests in its support on the frame and is comparatively loose. The results of the operation of the instrument are therefore largely due to the inertia of the slate casing, and probably to a considerable extent also to the simple agitation of the granular carbon contained in the button.

Having now fully described my invention, I claim 1. In a telephone transmitter a hollow block of slate forming the casing and side walls of the resistance containing chamber, said block containing a fixed electrode at the rear of said chamber, a vibratory electrode mounted and adapted to vibrate within the front opening of said chamber, and finely divided conducting material placed within said chamber and between said electrodes,

substantially as described.

2. In a variable resistance button for a transmitting telephone, the combination of a hollow block of slate forming the casing and side wall of the resistance containing chamber; 21. fixed electrode secured within said chamber and forming its rear wall or floor; a vibratory electrode mounted and adapted to vibrate within the front opening of said chamber; finely divided conducting material placed within said chamber, and between said electrodes; and a disk of fine wire gauze supporting the said vibratory electrode secured to the front of the casing and closing the said containing chamber; substantially as specified.

3. The combination in a telephone transmitter of a diaphragm, a variable resistance button mounted wholly upon said diaphragm, and alight back support also mounted on said diaphragm and delicately holding said button in place, substantially as described.

4. The combination in a telephone transmitter, of awooden diaphragm; a chambered button having front and back disk electrodes, a slate casing and side wall, and finely divided conducting material contained therein mounted as a whole on said diaphragm and having its front electrode attached to the center thereof; and a support also mounted wholly on said diaphragm, and engaging delicately with the rear of the said button and adapted to hold it in place substantially as specified.

5. In a telephone transmitter a diaphragm 10f wood held in place by spring pressure only; combined with a hollow button mounted thereon, the said button comprising a block of slate forming the casing and side wall of a containing chamber, a carbon disk secured therein and serving as the fixed electrode, a vibratory electrode secured to a flexible disk of wire gauze clamped to the front of said containing chamber, the said electrode being attached also to the center of the said Wooden diaphragm and adapted to participate in the vibrations thereof; granular conducting mate rial inclosed in said chamber; and a rear support for said button; substantially as described.

6. The combination in a telephone transmitter with the diaphragm, of a compound variable resistance button comprising a mass of finely divided conducting material in a loose or free state and a containing chamber therefor, having a fixed back electrode, a slate side wall and a vibratory electrode or front plate mounted on a flexible disk of fine wire gauze, and attached to the diaphragm center so as to vibrate therewith, and a support holding the said compound button in place, and itself mounted on the diaphragm, substantially as described.

7. The combination in a telephone transmitter with adiaphragm of wood held in place by spring pressure only; of a compound variable resistance button comprising a mass of finely divided conducting material in a loose or free state, and a containing chamber therefor, having a fixed back electrode, a slate side as described.

8. A granular carbon transmitting telephone comprising a frame or ring seat; a diaphragm, a chambered button containing granulated carbon mounted on said diaphragm and having a casing and side wall of slate for the said chamber, a rear wall of carbon constitutin g the fixed electrode and a front wall of carbon secured to a flexible disk of fine wire gauze forming the vibrating front electrode, the said gauze being clamped to the slate side wall, and the said front electrode being secured to the diaphragm center to vibrate therewith, and a light bridge also mounted on the diaphragm and delicately supporting the same, substantially as described.

9. A granular carbon transmitting telephone comprising a frame or ring seat of wood; a diaphragm of wood held in the said seat by spring pressure; a chambered button containing granular carbon mounted on said diaphragm and having a casing and side wall of slate for the said chamber, a rear wall of carbon constituting the fixed back electrode and a front Wall of carbon secured to a flexible disk of fine wire gauze forming the vibratory front electrode, the said gauze being clamped to the slate side wall, and the said front electrode being secured to s the diaphragm center to vibrate therewith; and a light bridge also mounted on the diaphragm and spanning the said button and delicately supporting the same, substantially as described.

In testimony whereof I have signed my name to this specification, in the presence oftwo subscribing witnesses, this 12th day of December, 1893. V

WILTON L. RICHARDS. Witnesses:

Gno. WILLIS PIERCE, VICTOR M. BERTHOLD. 

